Decolorization process



Aug. 3l, 1954 P. B. wElsz 2,687,990

DECOLORIZATION PROCESS Filed Nov. 28, 1950 26 o/L (HH/mf Z Patented Aug. 31, 1954 DECOLORIZATION PROCESS Paul B. Weisz, Pitman, N. J., assigner to Socony- Vacuum Oil Company, Incorporated, a corporation of New York Application November 28, 1950, Serial No. 198,018

8 Claims.

This invention relates to color refining of petroleum fractions. More particularly, the present invention is concerned with a method for decolorizing certain petroleum fractions characterized by the presence of polar colored components and containing a relatively high content of naphthenic acids, i. e., quantities of the order of 0.5 to 3 per cent by weight. Typical of the stocks which may be effectively decolorized by the process of this invention are untreated coastal oil distillates and distillate type fuel oils having an approximate boiling point range of 300 to 800 F.

The removal of substances producing color in petroleum fractions is generally understood to be dependent upon the phenomena known as adsorption. The effectiveness of oil refining operations employing adsorbent materials accordingly dependsl upon the characteristics and properties of the adsorbent materials used as well as upon the particular stock undergoing treatment. An ever present problem in the art is to develop improved adsorbents in order to obtain higher decolorization efficiency and increased commercial value in these operations. In one method for the decolorization of petroleum fractions, the oil to be decolorized is agitated with a nely divided adsorbent material for a suitable period of time, followed by separation of the decolorized oil from the spent adsorbent mass. Such procedures are generally referred to as Contact methods of decolorization. A second method for decolorizing oil stocks has involved percolating the stock through a column of particle-form adsorbent. These processes are referred to as percolation methods of decolorization. In either of the foregoing decolorizing procedures, it is essential that the adsorbent medium employed possess a high sorption capacity for the particular color bodies contained in the specic stock undergoing treatment.

The process of this invention is directed to the decolorization of certain oil distillates boiling between about 300 F. and about 800 F. and containing a naphthenic acid content of about 0.5 per cent by weight and greater. Such stocks have heretofore been decolorized with conventional clay-type adsorbents. Operations utilizing such adsorbents, however, have generally been conducted on a batch basis since the clay,`

after contact with the foregoing stock is ordinarily not subject to solvent regeneration. This invention accordingly has as its principal object the provision of an improved process foidecoloriz'ing petroleum fractions of the above type.

' cotton has been found to possess excellent capacity for sorbing color bodies from petroleum distillates having a relatively high naphthenic acid content. It has further been discovered that color bodies thus sorbed can be effectively removed by elutriation with a polar organic solvent and the color sorption capacity of the cotton can thus be regenerated.

Broadly, the present process comprises bringing the oil fraction to be decolorized into contact with the cotton adsorbent for a suitable period of time and thereafter effecting a separation of the decolorized oil from the spent cotton adsorbent. The method of this invention may be carried out either by a contact decolorization procedure wherein the cotton adsorbent is immersed and soaked the necessary time within the oil stock and thereafter removed by filtration or other feasible means or alternatively the decolorization may be accomplished in a percolation operation wherein the oil fraction undergoing treatment is permitted to percolate through a column packed with cotton. With the use' of either procedure, the cotton containing sorbed color bodies may be regenerated by elutriation of the spent adsorbent with an organic polar solvent, after which the cotton adsorbent is again ready for use.

The adsorbent employed in the present process is ordinary cotton, preferably in an unbleached condition, although bleaching of the cotton is not contemplated to affect its sorption capacity for removing color bodies from the particular stocks undergoing treatment. When employed in a percolation type operation, the cotton adsorbent is thoroughly tamped into place to prevent channeling of the oil stock passing therethrough. Generally the density of the cotton column through which the oil fraction percolates will be between about 0.1 and about 0.8 gram per cubic centimeter. The sorbing capacity for color bodies present lin the petroleum distillates treated by the method of this invention appears to be confined to the use of a fibrous adsorbent of cotton. Thus, other organic fibers, including wool, were found to be unsuitable as adsorbents for decolorizing the petroleum stocks treated by the instant process. 5 The petroleum fractions decolorized by the present method include crude oil distillates containing between abontfl" and aboutf pencentfff by weightcff. nafphthenic'lacids, havingva .boiling point range of 300 to 800 F. and an A. P. I. 10 gravity of between about 20 and about 40. Just as cotton appears to exhibit specific colonsorp.-y tion properties for stocks of the above'type; these stocks appear to be particularlylsusceptie. ble to decolorization by a cottonradsorbentzil' Thus, it has been noted that certain other petroleum fractions, such as acid-treated..stocks,..., are not appreciably decolorized by' the instant process. Treatment of such stocks accordingly'f is not within the purview 'of this invention. 20

The conditions. under...,whch .thepresentproc-f essis carriedoutmay vary` Widely,..depending-up+.. on the. nature and .degree of.. dis'co1oration-.of..the.r oil stock undergoing :treatment and upon..whether.` .Y it is.desired. to use a contact-Ona percolation-type ..25 operation.v Fora Contactoperationfthefoil stock. is brought into contactwith. cottonadsorbent and:. saidfcontact is. maintained fora sufficient ,periodr: of time to effect substantial removal..of...color..: bodies .contained therein...=.The.duration..of.such 30 contact. is .dependent .upon .the relative. propor tions.. `of oil .and adsorbent.. as ,.well f as upon. the. degree of ydiscoloration .of .the oil. .As a generale. rule,.the..larger the .amount-...of cottonadsorbent. present, .the shorter is 1 the. contact time .-required... 35 Under the. usual. .conditionsof .practicing .the .proc: l ess. of .this.invention, howevenemploying; the .contact technique, ,the .period .of `contact iwill gener-, ally .range f1'om..about. 2 to.aboutn15 hours. ...In order to bring about a moreelfectivecontactbef; 40 tween the cotton.. adsorbent and the ol"stocl ,.\the' mixture is ,ordinarilyI agitated by-.stirrng,-,shakv...

ing,` or other means .-during. the. aforementioned. f. period... Suchtreatments .are effected at=substan;-; tially. atmospheric A.pressure and -may be..carried.-..45 on atfambient or higher rtemperatures, generally. not exceedingA about r200.o .C;. VThe quantity.. of. ad-.\ -v sorbent employed: may.-.be. .of -the orderfof fromm. about,.-10 per .cent:to.about.200pencent or mores.Y by iweight. based...onv` the. quantity of. oil-:stockO treated,..depending.uporr the stateof .the `oilfstocl: and4 upon` the qualities desired-inthe resultingg decolorized product. .The decolorizedoil'isthereafter separated fromfthe. spent .cottorr by filtra-.2 u tion.. centrifuging, ;or. other. suitable mea-nsf: 0 For a percolation operationthel oil stock.is ine." i troduced into a verticalcolumn.packed,` with. cote.`4 ton..A adsorbent-and;` the .oilspermitteclsto percolate. t by gravitytherethrough. The.-.pa.cking densityw` and the length of thecolumrL-are \'so.eorrelatedf` that. oil emerging from: the bottom of. the columnis substantially free of color bodies without neces. sitating. fan.. unduly long, Jtirne. of? epercolation.:J Treatment is: effected.at;temperatureszfranging.-. from.. atmospheric.. to moderately elevated ,tem, 6D peratures not exceeding-.about.200 C. The opera--v tionzis generally carried out at'atmospheric pres-s l sure, .although` the application .of :pressure during. g percolationmay insome instances beifound yde." sirable. 70 With either.. of the: foregoing techniques,- the..V cotton :adsorbent containing. sorbed colon'bodies' maybe regenerated by elutriation with-an organic. polarsolvent. .,The. solvents .useful fonthis pure.

pose. should, .possess ,.at. .least some .mutual..solu 75 bility with the oil undergoing treatment and should be sufficiently volatile to be completely separable from the oil by distillation at relatively low temperatures. The solvent employed should be polar in nature since the color bodies removed from the adsorbent therewith are polar. The reason for mutual solubility of solvent and oil resides in =tlrernecessity forzthe' polar. solvent to penetrateandework "olf layers @Poil-'adhering to the cotton adsorbent. The elutriation will generally be carried out at atmospheric temperatures although in some instances slightly elevated temperatures not exceeding the boiling point of the parti-cular solvent: employed may be helpful in facilitatingztheremoval of color bodies. In particular; itnhas been'ffound that the lower alcohols and ,ketoneamaybefused with advantage as elutriants for the sorbed coloring matter. Thus, ethyl;.zeisopropyl, butyl, amyl, and isoamyl alcohols and such ketones asiacetone, methylethyl ketone;and-:methylisopropyl ketone 4may. be usedV advantageously.,-v These...solvents, together with.. other polarwsolvents. having .the above. dened characteristics..may` befnusedeither alone orafin.A combinationvto .provvide an.,eifective -elutriantmedium formegeneratingthe spentadsorbent ,by removing sorbedcolonbodies therefrom.: In some... instancesit has-.been found. desirable to rstawashx theucotton y.adsorbent'rf containing sorbed u colon bodies. with. an'. oil solvent,I suchy ascarbon tetrachlorides naphtha; -:etc., .to effect r removal. of oil adhering tosthe. adsorbent. and thereaftertore-r move the sorbed color bodies by extraction ,with onenf .the V.aforementioned ,-polar.y solvents.

Thetregeneratedcottonfadsorbent .may be used for...further; decolorization. Thesolvent solution containing, -the @coloringmatter previously removed treatedftoelfect recovery. of the solvent.. y. Such, treatmentbrdnarily: involvesfractionating -a solution of coloringfmatterg-driving ,the'solvent therefrom'asioverheadand;obtaining the coloring l, bodies: tas. residuei- Solvent vapor: .removed as overhead is condensed :and .may then; if desired. be used.-for. further :elutriation ofithe-,spent-adf `sorbenta f,

The processsdescribed above -conveniently adaptabieto ycontinuous; Y operation and'rsutable r f. systems lfor'carrying out such operation are shownk l in .thevfattached-` drawingf. Referring vmore 4par,- ticuiarly to.-Figure yl ofA the.drawing,.;.it .willbe.-.r seen thatA the foil: which .is tobefftreatedis con- A ductedsintoemixing ,.,tanlr1 l through conduit.2.f ThacOttOnfadsorbentfis ledf'intothemixing tank viacnletfpiper. ,f The. tank-is .'providedf'with a -z propeller agitator 4 which serves to intimately admix the-oil and adsorbent.'v After thorough adv mixturehasfbeenattained, valve 5 in the bottomA of the\mixing.tanklis opened 'and decolorized oil is permittedtodrain-from the'tankthrough out-A let pipep The z cotton adsorbent' isretained` in y; the mixing tank on slanted'. perforated'platerrl havingaa plurality. of. rollers. B aixed .thereto` ltol permitmovement ofthe cotton-adsorbent through a conduit 9 whenxvalve i0; is opened... The spent cottonv v adsorbent :passes falongpconduit 9, ther` movementI being facilitated by a pluralityy of:Y rollers. ;Il. The sorbentthereafter passes into... towerv l2, falling onto a slantedl perforated plates'. I3 likewise provided with a plurality of rollersl 4. i Polar `solvent is introduced intotowerf I Z'through-f pipes-l5 and;|6;and flows through the spentadf.. sorbent contained in the tower; removing sorbedf; color bodiesftherefrom`.-. The stream-of solvent containing the rcolonbodies-fso-removed-is conducted Ifrom-.the'bottomof towenl 2 through out-,fr

I8. The column is maintained at a temperature such that the solvent passes overhead as a vapor through pipe I9 while the coloring matter previously removed from the oil and the adsorbent collects in the bottom of column I8 and is lperiodically removed therefrom through pipe 20. The solvent vapor flowing through pipe I9 passes through condenser 2| wherein the solvent vapor is condensed. Liquid solvent ensuing from condenser 2| is recycled to tower I2 through pipe I6.

The cotton adsorbent so regenerated in tower I2, upon opening valve 22, moves by gravity from plate I3 along rollers I4 and passes through conduit 23 provided with a plurality of rollers 24 to facilitate movement of the cotton. Conduit 23 is heated by coils or other suitable means not shown, driving solvent from the cotton adsorbent passing therethrough as overhead vapor. This vapor passes through pipe 25 to condenser 2|. The dried regenerated cotton passes from conduit 23 into an air-lift 26 provided with a plurality of inlets 2'| for the introduction of high air pressure. The cotton is thus pneumatically elevated through air-lift 26 and recycled to mixing tank I, passing through inlet pipe 3.

Referring more particularly to Figure 2 of the drawing, wherein a suitable continuous percolation process is shown, 30 designates ka tower packed with cotton adsorbent. The oil charge to be treated is conducted into tower 30 through conduit 3|. The oil so charged percolates down through the tower and decolorized oil flows from the bottom of the tower through outlet pipe 32 provided with valve 33. After the oil charge has drained from the tower, valve 33 is closed and polar solvent is introduced into the tower through pipes 34 and 35. The solvent passes down through the spent cotton adsorbent contained in the tower, removing sorbed color bodies therefrom, and passes from the bottom of the tower through conduit 36 provided with a control valve 31. The solvent containing sorbed coloring matter is then conducted into fractionating column 38. The column is maintained at a temperature such that the solvent passes overhead as vapor through pipe 39 while the coloring matter previously removed from the oil and the adsorbent collects in the bottom of column 38 and is periodically removed therefrom through pipe 40. The solvent vapor owing through pipe 39 passes into condenser 4|, wherein the solvent vapor is condensed. Liquid solvent ensuing from condenser 4| is recycled to tower 30 through pipe 35. After regeneration of the cotton adsorbent, a further oil charge is introduced through conduit 3| and the oil percolates down through the tower, removing a certain amount of solvent from the wet adsorbent during its course of fiow. This oil, after percolation, is removed from thebottom of the tower through conduit 42 provided with control valve 43. The admixture of oil and solvent is led into fractionating column 44, which is maintained at a temperature such that the solvent passes overhead as vapor through pipe 45 while decolorized oil collects in the bottom of column 44 and is periodically removed therefrom through pipe 46. The solvent vapor flowing through pipe 45 passes into condenser 4I and then is recycled to tower 30 through pipe 35.

Having described the nature of this invention, the following specific but non-limiting examples will serve to illustrate the improved results attained in accordance with the instant process.

Eaiample 1 Eight hundred grams of a coastal distillate having an A. P. I. gravity of 25.7, a boiling range from 500 F. to 700 F., and a naphthenic acid content approximating 1 per cent by weight was percolated through a column 2 inches in diameter and 24 inches high, containing 160 grams of unbleached cotton. The temperature was maintained at about 20 C. and the rate of flow was about 1 fluid ounce per hour.

rIjhe oil before contact with the cotton adsorbent had a color (Lovibond) of 5 and after passing through the column of cotton adsorbent had a color (Lovibond) of 2.7.

Example 2 Five hundred c. c. of an oil having an A. P. I.

gravity of 25.7, a boiling range of from 500 to 700` F., and a naphthenic acid content approximating 1 per cent by weight was percolated through 80 grams of cotton contained in a column two inches in diameter and 24 inches high. Percolation was carried out at roo-m temperature and the rate of flow was about 1 uid ounce per hour.

The oil before contact With the cotton adsorbent had a color (Lovibond) of 5 and after percolation through the columnv of cotton had a color (Lovibond) of 3.2.

Two hundred c. c. of carbon tetrachloride were passed through the column of cotton adsorbent to remove oil adhering to the surface of the cotton. Thereafter, 500 c. c. of isopropyl alcohol were passed through the adsorbent column,'removing the sorbed color bodies. The cotton so treated was thereafter dried. Five hundred c. c. of fresh oil stock were again passed through the same column and the color of the oil after percolation was found to be 3 on the Lovibond scale.

Example 3 Two hundred seventy-five c. c. of a fuel oil boiling between about 330 and about 640 F. and having an A. P. I. gravity of about 31.3 and a naphthenic acid content of about 0.5 per cent by weight were percolated through a column 2 niches in diameter and 24 inches deep, containing 40 grams of unbleached cotton. Percolation was carried out at room temperature and the rate of percolation was about `1 uid ounce per hour. The oil after percolation through the column had a color (Lovibond) of 17. The charge stockhad a color (Lovibond) of 30.

From the foregoing examples, it will be seen that cottonpossesses a high color sorptive capacity for removing color bodies from mineral oil fractions characterized by a boiling point within the range of 300 to 800 F., an A. P. I. gravity within the range of 20 to 40 and a naphthenic acid content of between about 0.5 and aboutv 3 per cent by weight.

It is to be understood that the above description is merely illustrative of preferred embodiments of the invention, of which many variations may be made within the scope of the following claims by those skilled in the art without departing from the spirit thereof.

I claim:

1. A method for removing color bodies from an oil containing the same characterized by a boiling point range of between about 300 and about 800 F., an A. P. I. gravity of between about 20 and about 40, and a naphthenic acid content of between about 0.5 and about 3 per cent by weight, which comprises agitating said oil with ordinary cotton adsorbent to insure thorough admixture 2."A method. for. removing. color bodies frorn'an oil containing the same characterized by a boil-v ing point range of betweenabout 300'and. about 800"F.'," an A. P..I."gravity of between ab0ut.20 and., about 40, and a naphthenic acid. content of between about 0.5 'andabout 3 percent by weight, which comprises percolating said oil through a column .packed with. ordinary cotton adsorbent, collectingthe oil issuing from said column. and elu'triating thespent cotton with'a polar solvent.

3. 'A method for removing color bodies from an oil containing the same characterized by a boiling point range of betweerrxabut 300 and about 8005 F., an A. P. I. .gravity .of between about and. about.40,`and a naphthenic acid content of between about 0.5 and about'3 per cent by weight, whichlconiprises contacting said oil with ordinary cotton "adsorbent, separating lthe oil so treated from said adsorbent. and 'elutriating the spent cotton with'a polar solvent.

4. A 'method for removingcolor bodies from an oil containing the same characterized by .a boiling point range of Vbetween about 300 and about 800.F.,'an A. P.'I. gravity of between about 20 and about 40, Vand a naphthenic-,acid content of between about 0.5 .andfabout ,.3 per cent by weight, whichcomprises. contacting said oil with ordinary cotton adsorbent, separating the oil .so treated from said adsorbent, removing oil adheringto. said adsorbent with a solvent therefor and thereafter. elutriating the cotton adsorbent.

with -a polar solvent.

5. A. continuousprocess .for removing color bodies froman oil containing the same and characterized by. Aa boiling. range of betweenabout 300 and 800 F., an A. P. I. gravity of between about 20 and about 40z and anaphthenic acid contentof between about 0.5 and about 3 per centby. weight, which comprises contacting said oil .with ordinary cotton adsorbent, ltering the decolorized oil .from said cotton adsorbent, elutriating-th spent `cotton with a polar solvent, drying vthe cotton adsorbent so regenerated, recycling the regenerated cotton .to further contact with the original oi1,.separating the solvent solution ,of.color bodies andrecycling said separated sol-ventto. vContact .with the. aforesaid. spent cotton.v

6. A continuous process..for removing color bodiesfroman oil containing the same and characterized by. a boiling range of between about 300 and.800-F., an A.. P., I. gravity of between about 20.and. about 40 anda naphthenic acid content of.

between about 0.5 and about 3 per cent by weight, which comprises agitating said. oil with ordinary cotton adsorbent for a suitable period of time to sorb `colora-bodies:fthereirom;: ltering A:thev 'oilnso'v decolorizedy from saidzcottcnelutriating the spent. cottoniwith, a polarfxsolvent, 'drying 'the' cotton-tt so regenerated, recycling theregenerated cottont. 'to further contact with theoriginal oil','separating the. solvent solution of .'color bodies and recycling' i.

said' 'separated' solvent;to .contact with the afore-i said spent fcotton.V

'7. A -continuous process for :removing :colors:` rbodiesffroman'oil containing thesame and characterizedfby a boiling range of between about 300x and 800 AFJan A.'P..I. gravity of between .about 20'and. about 40.and"a naphtheni'c;acidxcontentx' of'betweenzaboutzo and abouti percent by. i' Weight; which'. comprises .percolatingsaidzoill through :a column itpacked with 'ordinarys" ad-f sorbentcotton;:collectingthe: decolorized oil issuing from said column,relutriating theLspentcot r tonv witha polarv solvent, separating thessolv'ent'.-

solution of. color bodies;.-'andxi'ecyciing said'. sep-' i aratedf solvent .to said column.` L.

8. A continuous :processsfor removing' color bodies fromfan oil..'containing y the 'same and".

characterized by a boiling range;of.between about' 300'. and 800.F., an;'A. P. I. gravity 'of between about 20 and about 40 and a naphthenic acidv contentzof between about.0.5 and about 3 per cent lby weight, which 'comprises `percolating f saidy 'oil'A through a columnpacked .with' ordinary 'cotton adsorbent, collectingthe decolorized oil issuing from said column, elutriating the spent cotton with a polarsolvent, separating the solvent solu'` l tion of color bodies so obtained, contacting the' v regenerated cotton adsorbent with a fresh 'charge' of oil', separating the mixture ofl oil and solvent' issuing from said column, collecting the decolor'Y ized oil' obtained asa result of said separation1 and`` recycling .the separated solvent to contact with' the spent cotton adsorbent'.

References Cited in the file` of this patent f UNITED STATESLPATENTSv Numberr Name t Date 854,057 Ryan etal: May21,1907: 1,450,617v Smith Y Apr'. 3, 41923:',- 2,106,071 Stanton Jan. 18,1938- f 2,219,101- Finwall Oct; 22,' 1940* 2,470,339y Claussen et al;v May 17,.'1949ff FOREIGN PATENTS Number Country Date 79,814. Austria Jan.,26, I1920..

OTHER REFERENCES v' Sachanen, .The Chemical` Constituents of Petroleum, Reinhold Publishing Corp., 330 42nd l Street, New York,"N.' Y.;4 pagesA 320 and k321- (1945)'. 

1. A METHOD FOR REMOVING COLOR BODIES FROM AN OIL CONTAINING THE SAME CHARACTERIZED BY A BOILING POINT RANGE OF BETWEEN ABOUT 300 AND ABOUT 800* .,A ND A. P. I. GRAVITY OF BETWEEN ABOUT 20 AND ABOUT 40, AND A NAPHTHENIC ACID CONTENT OF BETWEEN ABOUT 0.5 AND ABOUT 3 PER CENT BY WEIGHT, WHICH COMPRISES AGITATING SAID OIL WITH ORDINARY COTTON ADSORBENT TO INSURE THOROUGH ADMIXITURE OF COTTON AND ELURIATING THE SPENT COTTON WITH A POLAR SOLVENT. 